All popup IFRAMEs are created with attribute scrolling="no". If the content inside the IFRAME is "bigger" than the actual modal view (in it's maximum size), user should be able to scroll the content. This works properly in Firefox for instance but Chrome ignores the overflow-y:scroll CSS and disables scrolling of the IFRAME. There are possible CSS fixes available but none work nicely in all browsers.

Suggested fix is to set scrolling attribute to 'auto' as it's the default state and only explicitly set to 'no'.

I've tested this with a number of themes and, depending on how they style things like exposed views filters, the buttons can be pushed off of the page and require a middle mouse button click to scroll to.

This patch guarantees that users will still be able to use the buttons regardless of which administrative theme they are using. It would also enable the extra "scrollbox" div on the library tab to be removed.

The patch applied cleanly with an offset. I've attached an image showing how the buttons can be hidden (using bartik as an example) and how the patch enables the iframe to be scrolled so the buttons can be reached.

I think that this is the best option, short of removing the ability to select a custom administration theme.